1965 Dodge 383 Motor Bogging Down Under Hard Acceleration

[65Polara383]

I posted recently about a similar issue I was having with my car, possibly the same one.
Since then, I have replaced the fuel pump pushrod, verified the function of my fuel pump, and installed an Edelbrock AVS2 650 (Which runs perfectly).

The issue no longer occurs when normally accelerating up hills and no longer leaves the car dead on the side of the road. But any time I accelerate with more than about half-throttle the car falls flat on its face, way less power than under normal acceleration, and then after a few seconds starts bogging down like it is running out of fuel.
Letting off the gas completely for a little bit fixes the problem.

I would like to get this figured out, since I cant even enjoy the performance of my new 4-barrel carb.
Other than this it runs great though. Smooth idle, great torque when accelerating normally, and fuel-injection-like throttle response.

Refer to my older post for what we have already ruled out.
Thanks for any help you guys can provide.

 

[CBODY67]

For general principles, get a screwdriver and loosen the cap over one of the power pistons. If as you slowly loosen the screw, the cover wants to come upward, that's a good sign. Continue to loosen the screw until it is out (a magnetic screwdriver might help, so you don't drop the screw). Then remove the cap and place it and the screw in a cup for safe keeping. Then extract the power piston and spring under it, with the metering rod attached.

On the side of the metering rod are some stamped numbers, like xx-xxx. That's the ID for the rod. Compare that the specs for that carburetor. Also note the color of the spring. Then put everything back together.

As the manifold vac decreases with additional throttle, the power piston moves upward in its bore, enriching the mixture as it does. So, as long as it is free and the spring and rod are correct, that would mean a "supply issue" rather than a "carburetor issue". As to the fuel system, to me.

Also, understand that fuel issues and ignition issues can act the same. So double-check the distributor and coil for correct operation. Plus the strength of the spark under load.

Can you duplicate "the bog" under load, loading the engine against the foot brake in "D"? Will the engine back-fire if you suddenly go to WOT at cruise? Or at least bog immediately, or will the bog happen as the length of engine load increases?

Take care,
CBODY67

 

[65Polara383]

I will check the metering rod in the carb, it is in great condition though.

The distributor is in good condition, the ignition system is a Pertronix Ignitor II with the Flamethrower II coil, I will confirm voltage and spark soon and get back to you.

I can easily duplicate the bogging by accelerating at WOT for about 5-10 seconds.
The engine does not back-fire at all, not through the carb or the exhaust.

I had forgotten to mention that the bogging only happens if I let the motor rev above ~3500RPM.

 

[65Polara383]

Spark is good, coil voltage is 13-14V.

The car does spit some black smoke from the exhaust when the throttle is applied though.
Probably just running rich.

 

[CBODY67]

Usually "bogging down" indicates a "lean mixture" from lack of fuel. That is different from a rich condition where black smoke comes out of the exhaust. They act differently, from my experiences.

You probably should be smelling hydrocarbons on the engine oil dipstick and the motor oil should be black from fuel dilution, generally. As the spark plugs should be sooty, too, possibly? Pull one out that is easy to get to, like #1 or #3 to see what color the ceramic insulator might be, for good measure.

Thanks for the reminder about the upgraded ign system. How do you have the base ignition timing set? What number of degrees advanced from TDC?

Thanks,
DBODY67

 

[65Polara383]

I went to verify the tuning on the carburetor, and realized that I had the mixture screws about 3 turns from where it starts to lean out, I am going to take it for a drive and get back to you on the results. That might have fixed it.

On my old carburetor the plugs were a perfect tan color and the oil had no fuel smell whatsoever.

Last time I adjusted the ignition timing I did it by ear/feel, the car runs and idles great but I am sure there is more power I can get from it if I use a timing light.

 

[65Polara383]

I found the problem, the fuel is boiling in the lines.

I am making a new post for this issue.

 

[MoparapoM]

Following up on a Statement you made earlier in this posting. Your 'Coil Voltage' is incorrect, if your Ignition is not modified, it should be going through a Ballast Resistor and reduced to something around 7 Volts.

Bruce

 

[Big_John]

Following up on a Statement you made earlier in this posting. Your 'Coil Voltage' is incorrect, if your Ignition is not modified, it should be going through a Ballast Resistor and reduced to something around 7 Volts.

Bruce

You don't need the ballast resistor with the Pertronix ignition.

 

[MoparapoM]

That may be so... However the stock MoPar Ignition Coil DOES require a voltage reduction.

B

 

[Big_John]

That may be so... However the stock MoPar Ignition Coil DOES require a voltage reduction.

B

You really have to read through the thread. He's using a Flamethrower II coil.

If you look at the Pertronix install instructions, you'll see you don't need the ballast resistor.

 

[MoparapoM]

Sorry, I started on another thread, then tripped and fell into this one! It's such a common issue for folks to install a 'GM' version Coil, I can't count how many times I've I've had to correct that...

B

 

[Big_John]

Sorry, I started on another thread, then tripped and fell into this one! It's such a common issue for folks to install a 'GM' version Coil, I can't count how many times I've I've had to correct that...

B

Sometimes it's tough to keep it all straight. I've caught myself responding to the wrong thread many times.